The purpose of this investigation is to elucidate the function of basophils and mast cells in cell-mediated hypersensitivity reactions, particularly with regard to an understanding of the role of these cells in immunologic tumor rejection. The experiments proposed will make use of a tissue culture system and a combined biochemical, morphologic, and immunologic approach to determine; (1). Whether sensitized lymphocytes or their products affect histamine synthesis and/or release in basophils/mast cells. (2) The mechanism of mediator release from basophils/mast cells under circumstances which avoid explosive degranulation. (3). The effects of basophils/mast cells and their pharmacologic mediators on tumor target cells.